Liquid pumping apparatus



21, 1964 E. D. SIMONS ETAL 3,118,491

I LIQUID PUMPING APPARATUS Filed Dec. 13, 1960 4 Sheets-Sheet 1 FIG].

J 1964 E. D. SIMONS ETAL LIQUID PUMPING APPARATUS 4 Sheets-Sheet 2 FiledDec. 13, 1960 1964 E. D. slMoNs ETAL LIQUID PUMPING APPARATUS 4Sheets-Sheet 3 Filed Dec. 15, 1960 H54 7 Exam/vat? .2

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Jan. 21, 1964 E. D. SIMONS ETAL LIQUID PUMPING APPARATUS 4 Sheets-Sheet4 Filed Dec. 13, 1960 a2 s4 s5 67 a: 6/ 59// $3 42 A Inn/9 United StatesPatent 3,118,491 LIQUID PUMPING APPARATUS Ernest D. Simons and StanleyR. Tyler, (Iheltenham, England, assignors to Dowty Fuel System Limited,Cheltenham, England, a British company Filed Dec. 13, 1960, Ser. No.75,593 Claims priority, application Great Britain Dec. 15, 1959 3Claims. ((31. 158-365) This invention relates to pumping apparatus. Theobject of the present invention is to provide a pumping apparatuscapable of the delivery of liquid at widely varying pressures and flowrates to a hydraulic load. An example of pumping apparatus to which theinvention may be applied is the pumping apparatus used on an aircraft tosupply the burner nozzles of a gas turbine engine.

In accordance with the present invention a liquid pumping apparatus fordelivery of liquid at widely varying pressures and flow rates to ahydraulic load comprises a main pumping and metering unit capable ofpumping any desired flow rate of liquid within a lower pressure range,an auxiliary pump of the centrifugal type, and valve means operative bya pressure in the hydraulic load or by the pressure in the output of themain unit to connect the main unit output either directly to the load atlower pressures or to pass it through the centrifugal pump to the loadif higher pressures become necessary. Where the load takes the form ofspill spray nozzles which require a high pressure supply flow and alower pressure zone to which spill flow may return, the auxiliarycentrifugal pump may be connected to the spill burners to receive thespill flow and to pump it at a higher pressure for supply to the spillnozzles. For this purpose the auxiliary centrifugal pump may be providedwith an auxiliary port giving access to the pump impeller at a positionradially between the central inlet and the peripheral outlet, the supplyto the spill nozzles then coming from the peripheral outlet and thespill return entering the impeller at the auxiliary port. The output ofthe main unit is then preferably connectable by the valve meansalternatively to the centrifugal pump inlet or to the auxiliary portdepending on whether a higher or lower range of pressures are requiredin the supply pipe to the nozzles. The main unit may comprise a variablepositive displacement pump having metering means to control displacementto give the required rate of liquid flow. Alternatively, the main unitmay comprise a fixed positive displacement pump having a by-pass valveadjustable by flow metering means to give the required rate of flow.Again the main unit may comprise a centrifugal pump having a variablerestrictor controlled by the metering means in series with its inlet oroutlet ports. The auxiliary centrifugal pump may be arranged foroperation over part or the whole of its range as a vapour core pump inwhich the liquid forms an annulus within the pump casing whose radialdepth determines the pressure at the output and at the auxiliary port ifprovided. The valve means may comprise a simple changeover valve toconnect the output of the main unit alternatively to the input or outputof the auxiliary centrifugal pump in accordance with pressure at theoutput from the auxiliary pump which directly feeds the load.Alternatively, the valve means may operate to disconnect all ports ofthe auxiliary pump and to connect the main unit directly to the load inthe lower pressure range, the valve also acting in this condition toconnect the output of the auxiliary pump to a low pressure zone so thatthe pump may empty and thus take substantially no power to drive therotor. Again, alternatively, the valve means may comprise a pressuresensitive valve to connect the main unit output to the input of theauxiliary centrifugal pump when the pressure of the main output exceedsits predetermined value, a non-return valve being provided 3,113,491Patented Jan. 21, 1984 to connect the main unit output With theauxiliary centrifugal output whereby the main unit output may feed theload directly until the pressure switches the main output to the inputof the auxiliary centrifugal pump, the non-return valve then closingautomatically because of the higher pressure developed at the output ofthe auxiliary pump over and above the pressure of the output of the mainunit.

Various examples of the invention will now be described With referenceto the accompanying drawings in which:

FIGURES 1, 2 and 3 are diagrammatic representations of three separateexamples particularly illustrating the valve means;

FIGURE 4 is a more detailed diagrammatic representation of the mainpumping unit usable in any of the examples of FIGURES 1 to 3; and

FIGURE 5 is a detailed diagrammatic representation of an alternativepump for use in the main pump unit of FIGURE 4.

Reference is made initially to FIGURE 1. Hydraulic liquid is suppliedfrom a tank 1 to a supply pump 2 which may be of the variable positivedisplacement type or the fixed positive displacement type. Output fromthe supply pump 2 passes to a metering control 3 which measures the flowrate of liquid from the supply pump 2 and acts to control the output asdescribed with reference to FIG- URE 4 or FIGURE 5 to ensure that adesired flow rate is delivered. The supply pump 2 is capable ofgenerating a reasonable pressure, but where a large total pressure rangeof hydraulic liquid is required it may not be possible to rely on asingle positive displacement pump to supply liquid at the higherpressures. Alternatively, the drive for the supply pump 2 may be of alimited power capacity which will prevent the obtaining of higherpressures. The supply pump 2 and the metering control 3 together formthe main unit which supplies liquid at a selected flow rate but only upto a medium pressure level. The output from the main unit passes throughpipe 4 to a piston valve 5 comprising a cylinder 6 within which a spoolvalve 7 is slidable. The pipe 4 opens at a port 8 in the cylinder 6 at aposition where liquid flow is controlled by the land 9, so that in theuppermost position of the spool valve against an upper stop 11 aconnection is provided from port 8 to a port 12 leading to the inlet ofthe auxiliary pump 13, whilst in the lower position of the valve 7against the lower stop 14, the output of port 8 may flow into the port15 from which pipe 16 extends to the hydraulic load. The upper land 17of the valve 7 in the uppermost position connects a port 18 carryingoutput from the pump 13 to the port 15. The land 17 in its lower mostposition cuts off the flow passage between ports 18 and 15 and opens aflow passage from the port 18 to a port 19 which carries liquid to a lowpressure zone at the inlet to supply pump 2. The lower land 21 of thespool valve 7 isolates the lower end of the cylinder 5 which isconnected by a pipe 22 to the output pipe 16 so that the pressure in theoutput pipe 16 may act over the lower surface of the land 21. The forceexerted on the piston valve 7 is opposed by the compression of a spring23 located at the upper end of the piston valve 7. The spring 23 is alow rate highly compressed spring so as to allow movement of the pistonvalve 7 from one stop to the other when the pressure in the pipe 16 isabove or below a predetermined pressure. The auxiliary pump 13 comprisesa suitably shaped chamber 24 within which a centrifugal pump rotor 25 isrotat ably mounted for drive by a shaft 26.

The apparatus as described in FIGURE 1 may be used for the supply offuel to a gas turbine engine, the pipes 16 supplying burner nozzles of asimplex type. The metering control 3 is adjustable to select any desiredflow and usually, although not necessarily, the desired flow rate willdetermine the pressure that must exist in the output pipe 16 necessaryto cause the desired flow rate to pass through the load. If the pressurerequired in the pipe 16 is low, i.e. below the predetermined pressure,the piston valve 7 will be in its lower position against stop 14 underthe action of spring 23 and the output of the main unit through the pipe4 will then enter by port 8 into the space between lands 9 and 17 andleave through the output pipe 16. In this position of the valve theinlet 12 to the centrifugal pump 13 will be closed and the outlet 18 ofthe centrifugal pump will be connected through port 19 back to the inletof the supply pump 2. In this way the pump 13 will be empty, andalthough the rotor is driven very little power will be consumed. Whenthe pressure exceeds the predetermined value in the output pipe 16 thepiston valve 7 will move upwardly against the load of spring 23 to causeport 8 to be connected to port 12 and port 18 to port 15. Thus, theoutput liquid from the main unit will enter the auxiliary pump 13 and bedelivered from this pump through ports 18 and to the output pipe 16. Theliquid within the pump 13 will assume an annular form within the pumpcasing 24 whose radial depth will determine the pressure existing withinthe output pipe 16. The pressure in the pipe 4 will drop to a low valueapproximating to the vapor pressure of the liquid being pumped. The pump13 is, of course, of such size and driven at such a speed that it isfully capable of supplying the maximum liquid fiow rate at the maximumpressure desired from the whole apparatus.

Reference is now made to FIGURE 2 of the accompanying drawings wherepossible similar reference numerals will be used. This example isparticularly intended for the supply of fuel to spill spray nozzles inthe combustion chambers of an aircraft gas turbine engine. Fuel iscontained within a tank 1 and is normally drawn from the tank by asupply pump 2 of the positive displacement type and then fed through ametering control 3 which may act as ascribed with reference to eitherFIGURE 4 or FIGURE 5. After passing the metering control 3 the fuel isat medium pressure and is then passed through a heat exchanger 27 forthe cooling of liquids used in the aircraft which might reach anundesirable high temperature for example engine lubricating oil. Againthe supply pump 2 and the metering control 3 forms the main unit and theoutput is fed to pipe The auxiliary centrifugal pump 13 comprises arotor 25 rotatable by shaft 26 within a chamber 24. The rotor 25 is ofthe unshrouded type and at a position in the casing between theperipheral outlet port 28 and the inlet port 29, an auxiliary port 31 isprovided which ovens on to the vanes of the impeller 25. A piston valve5 is provided comprising a piston valve member 7 siidably mounted withina cylinder 6, the pipe 4 opening to a port 8 in the wall of the cylinder6. There is, however, some difference from the previous example in theconstruction of the valve 5. The valve member 7 comprises a pair ofspaced lands 32 and 33 of which the lower land 32 is sufficiently largeto close the passage between the port 8 and the port 12 which leads tothe inlet of the pump 13. The upper end of the cylinder 6 is connectedto the port 31 whilst at the lower end of the cylinder 6 a spring 23 isprovided which urges the valve member 7 upwardly. The lower end of thecylinder 6 is connected by a pipe 22 to the inlet of the pump 2. Theport 3 1 in the pump casing communicates by a pipe 34 with the spillconnections of a plurality of spill spray nozzles of which one isdiagrammatically indicated at 3-3. The output port 28 of the auxiliarycentrifugal pump communicates with a pipe 35 which feeds the main supplyconnection of the spill spray nozzles. A non-return valve 36interconnects the spill passage 34 with the output pipe 4 from the mainunit.

In normal operation of the example in FIGURE 2 at low rates of flow themetered output of the main unit passing through pipe 4 will passdirectly through nonreturn valve 36 into the spill passage 34. In thispa sage fuel will fiow to the auxiliary port 31 of the pump 13 and willbe centrifuged to the output port 28 whence it will flow at a higherpressure through the pipe 35 to the spill nozzle 30. The liquid withinthe pump chamber 24 may either completely fill the space in which theimpeller rotates or, alternatively, if sufficient pressure may be givento the liquid by the rotor a liquid annulus may be formed within thechamber having a vapour core, radial depth of the annulus givingpressures at the ports 28 and 31 suitable for the supply and spillpassages 35 and 34 of the spill nozzles. As the fuel flow rate isincreased by the action of the metering control 3 pressures in thesystem will rise and in particular pressure in port 31, which acts onthe upper end of valve member 7 will urge this latter against the spring23 to open the port 8 to the port 12 to allow flow from the pipe 4 tothe inlet 29 of the centrifugal pump 13. The pressure rise developed inthe centrifugal pump between the inlet port 29 and the auxiliary port 31will thus be added to the pressure in the pipe 4 with the result thatthe non-return valve 36 will close and liquid at higher pressures willthen pass through the pipes 34 and 35. Depending on the opening allowedbetween the ports 8 and 12 by the valve member 7 the pressure in thepipe 4 is controlled in a predetermined manner such that it does notdrop to a particularly low value, but at the same time it isconsiderably l0\ 'er than the maximum pressure that may be developed bythe pump 2. The auxiliary centrifugal pump may operate either completelyfull of liquid or, alternatively, with a vapour core. In this lattercase the pressure at the end of the inlet port 29 will be substantiallyzero and any pressure generated by the supply pump 2 for feeding to pipe4 will be lost as pressure drop between ports 8 and 12 of valve 5. Thus,the pump 13 will supply the entire operating pres sure for the spillspray nozzles.

Reference is now made to FIGURE 3 of the accompanying drawings and againsimilar references will be used as in the previous two figures wherepossible. The difference in the arrangements of FIGURE 3 from thearrangement of FIGURE 2 lies in the construction of the valve 5. Apiston valve member is no longer used but it is replaced by a simplepiston 37 having a hollow interior constantly in communication with theport 8 and a graduated aperture 38 for co-operation with port 12, sothat a graduated restriction of fuel flow from port 8 to port 12 isobtained with movement of the iston member 37, against the spring 23,which is in this instance a low rate a highly compressed spring. Thepressure acting on the piston to urge it against the spring 23 is thepressure existing in pipe 4. The auxiliary centrifugal pump 13 isarranged to operate as a vapour core pump or as a fully primedcentrifugal pump depending on operating conditions. Other than for thechanges effective to the valve 5 the arrangement of FIGURE 3 correspondswith the arrangement of FIGURE 2.

In operation at low flow rates and pressures the output from the mainunit passes from pipe 4 through non return valve 36 into the spill h wline 34 in which fuel flows back from the spray nozzles to the auxiliaryport 31 in the centrifugal pump. The rising pressure between port 31 andport 28 gives the necessary pressure increase between the passages 34and 35. In this lower flow rate stage liquid from port 31 will enter thechamber 24 which will give a vapour core so that the radial depth ofliquid from the core to the port 31 balances the pressure existing inthe delivery pipe 4 from the main unit. As higher rates of flow andhigher pressures are selected the output pressure in pipe 4 acts on thepiston 37 to urge it down against spring 23 to open the restricted flowpath thus increasing the radial depth of liquid inwardly at port 31 toincrease the pressure in pipes 34 and to a value of that existing in thepipe 4. In

Reference is now made to FIGURE 4 of the accom-.

panying drawings, which illustrates one form of metering control 3 andits control of the supply pump 2'. In this control the supply pump isassumed to be of the variable displacement kind and displacement iscontrolled by an angularly movable lever 41. The lever is moved by aservo motor 42 comprising a cylinder 43 and a piston 44, sliding thereinfrom which a piston rod .5 extends for pivotal connection to a lever 41.A spring 46 acts on the piston 44 to urge it to the positionrepresenting minimum displacement to the pump 2. A pipe 47 carriesliquid under pressure as delivered by pump 2 to pipe 48, and it passesthrough a restrictor 49 to the right hand end of cylinder 43. Fromcylinder 43 a pipe 51 extends into the metering control 3. Within themetering control 3 a passage 43 extends to an adjustable throttle 52,and fuel having flowed past this throttle enters the output pipe 4 fromthe metering control. The throttle 52 is adjusted by rack and pinion 53and 54 which in turn are adjusted by an external lever 55. The pressuredrop occurring at the throttle 52 is fed by means of pipes 56 and 5'7 topressure pads 53 and 59, which are joined together by a rod 61. Theresultant force exerted on rod 61 is transferred by a pin 62 to one endof a lever 63 mounted within a chamber 64 in the control 3. The forceexerted on the lever by the pin 62 is opposed by a compression spring 65acting oppositely on the lever about its fulcrum 66. The lever controlsescape of fuel from a vent 67 formed at the end of the pipe 51. Fuelentering chamber 64 from vent 67 escapes to a low pressure zone througha pipe 70.

In operation the fuel escaping from vent 67 will have passed through therestrictor 49 and thus the pressure acting on piston 44 to urge itagainst spring 46 will be determined by the escape flow permitted fromvent 67. A very small movement of the lever 63 will make considerablevariations in the escape flow from vent 67 and thus is capable ofmovement of piston 44. At a position of balance where the escape fromthe vent 67 determines a pressure in the cylinder 43 its balance is aspring 46, it can be seen that it is necessary for the spring 65 tobalance exactly against the load exerted by the opposed pressure pads 58and 59. It is therefore clear that the spring 65 will act to controlmovement of lever 63 to adjust the displacement of the pump 2 so thatthe flow rate through the throttle 52 causes a certain pressure drop atthe throttle 52 to occur. If the throttle 52 is adjusted by lever 55 acontrol as described will adjust the flow rate to retain the samepressure drop at the throttle 52. It will be clear that the meteringcontrol as described will enable any predetermined flow rate to beaccurately maintained.

Reference is now made to FIGURE 5 which discloses an alternativearrangement for the supply pump 2" to that disclosed in FIGURE 4. Inthis arrangement the pump 2" is of fixed positive displacement and aby-pass valve 68 is provided to adjustably by-pass fuel from thedelivery of the pump in order to determine a flow rate at the outputpassage 4. The by-pass valve comprises a bypass valve member 69 capableof axial movement to adjust the throttle flow passage between two ports71 and 72 in the valve 68. Port 71 is connected to the delivery passage48 of the pump 2 whilst port 72 is connected to the inlet passage to thepump 2". Piston valve 69 is adjusted by a servo piston 73 carried withinservo cylinder 74. Pressure liquid from the delivery of the pump 2" iscarried through pipe 75 to the lower end of cylinder 74 and through arestrictor '76 to the upper end of cylinder 7%. Pipe 51 extends from theupper end of cylinder 74 to the vent 67 in the metering control 3. Theescape of liquid from the vent 67 determines a pressure drop inrestrictor 76 which enables a force balance to be obtained between thehigher pressure acting over the lower smaller area piston 73 and thereduced pressure acting over the upper full area of this piston. For aposition of balance a particular position of the lever 63 in themetering control 3 is necessary, which will then determine an opening ofthe piston valve member 69 and of the by-pass flow rate from thedelivery of the pump 2", the remainder of the delivery then forming thecontrolled output through the pipe 4.

The main pumping and metering unit may be formed by Way of example asshown in either FIGURE 4 or FEGURE 5, and either of these arrangementsmay be included in the examples of the invention described withreference to FIGURES l, 2 or 3.

We claim as our invention:

1. In combination with a hydraulic load, a main pumping and meteringunit including a positive displacement pump and drive means therefor,which unit is alone only capable of pumping at required flow rates up toa predetermined high load pressure, an auxiliary pump of the centrifugaltype which is capable of pumping at said required flow rates againstload pressures in excess of said high load pressure, means defining twoflow paths between the main pumping and metering unit and the load, atleast one of which passes through the centrifugal pump, and valve meansoperative to route the main unit flow through the other of the flowpaths so long as the pressure applied by the unit remains below saidhigh load pressure and to divert flow through said one flow path whenthe pressure exceeds said high load pressure.

2. The combination according to claim 1 wherein the centrifugal pump isequipped with a peripheral outlet having a connection with the load, andwith a pair of inlets having a connection with the main pumping andmetering unit, one of which inlets is positioned centrally of thecentrifugal pump and the other of which is positioned relativelyradially intermediate the outlet and said one inlet thereof; and whereinthe valve means is opera tive to route the main unit fiow through theother of the centrifugal pump inlets so long as the pressure applied bythe inlet thereof when the pressure exceeds said high load unit remainsbelow said high load pressure and to divert flow through said onepressure.

3. The combination according to claim 2. wherein the hydraulic loadincludes a spill spray nozzle the inlet of which is connected with theoutlet of the centrifugal pump, and the spill return of which isconnected with the other of said inlets in the centrifugal pump.

References (Jited in the file of this patent UNITED STATES PATENTS868,718 Smith Oct. 22, 1907 1,049,894 Merrill Jan. 7, 1913 2,720,256Pearson Oct. 11, 1955 2,916,875 Morley et a1 Dec. 15, 1959 3,026,929Burns Mar. 27, 1962 FOREIGN PATENTS 750,909 Great Britain June 20, 19561,184,654 France Feb. 9, 1959 UNITED STATES PATENT OFFICE CERTIFICATE OFCORRECTION :Patent No., 3,, ll8 49l January 21, 1964 Ernest DO Simons etal,

It is hereby certified that error appears in the above numbered patentrequiring correction and that the said Letters Patent should read ascorrected below.

Column 6 line 5O beginning with "the inlet thereof" strike out all toand including "said one pressureo" in line 52 same column 6, and insertinstead the unit remains below said high load pressure and to divertflow through said one inlet thereof when the pressure exceeds said highload pressure Signed and sealed this 16th day of June 1964- (SEAL)Attest:

EDWARD J. BRENNER Commissioner of Patents ERNEST W. SWIDER AttestingOfficer

1. IN COMBINATION WITH A HYDRAULIC LOAD, A MAIN PUMPING AND METERINGUNIT INCLUDING A POSITIVE DISPLACEMENT PUMP AND DRIVE MEANS THEREFOR,WHICH UNIT IS ALONE ONLY CAPABLE OF PUMPING AT REQUIRED FLOW RATES UP TOA PREDETERMINED HIGH LOAD PRESSURE, AN AUXILIARY PUMP OF THE CENTRIFUGALTYPE WHICH IS CAPABLE OF PUMPING AT SAID REQUIRED FLOW RATES AGAINSTLOAD PRESSURES IN EXCESS OF SAID HIGH LOAD PRESSURE, MEANS DEFINING TWOFLOW PATHS BETWEEN THE MAIN PUMPING AND METERING UNIT AND THE LOAD, ATLEAST ONE OF WHICH PASSES THROUGH THE CENTRIFUGAL PUMP, AND VALVE MEANSOPERATIVE TO ROUTE THE MAIN UNIT FLOW THROUGH THE OTHER OF THE FLOWPATHS SO LONG AS THE PRESSURE APPLIED BY THE UNIT REMAINS BELOW SAIDHIGH LOAD PRESSURE AND TO DIVERT FLOW THROUGH SAID ONE FLOW PATH WHENTHE PRESSURE EXCEEDS SAID HIGH LOAD PRESSURE.